Chromatic interocular-switch rivalry.

Department of Psychology, The University of Chicago, Chicago, IL, USA.

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Department of Psychology, Department of Ophthalmology & Visual Science, and Institute for Mind & Biology, The University of Chicago, Chicago, IL, USA.

Abstract

Interocular-switch rivalry (also known as stimulus rivalry) is a kind of binocular rivalry in which two rivalrous images are swapped between the eyes several times a second. The result is stable periods of one image and then the other, with stable intervals that span many eye swaps (Logothetis, Leopold, & Sheinberg, 1996). Previous work used this close kin of binocular rivalry with rivalrous forms. Experiments here test whether chromatic interocular-switch rivalry, in which the swapped stimuli differ in only chromaticity, results in slow alternation between two colors. Swapping equiluminant rivalrous chromaticities at 3.75 Hz resulted in slow perceptual color alternation, with one or the other color often continuously visible for two seconds or longer (during which there were 15+ eye swaps). A well-known theory for sustained percepts from interocular-switch rivalry with form is inhibitory competition between binocular neurons driven by monocular neurons with matched orientation tuning in each eye; such binocular neurons would produce a stable response when a given orientation is swapped between the eyes. A similar model can account for the percepts here from chromatic interocular-switch rivalry and is underpinned by the neurophysiological finding that color-preferring binocular neurons are driven by monocular neurons from each eye with well-matched chromatic selectivity (Peirce, Solomon, Forte, & Lennie, 2008). In contrast to chromatic interocular-switch rivalry, luminance interocular-switch rivalry with swapped stimuli that differ in only luminance did not result in slowly alternating percepts of different brightnesses.

The equiluminant plane of the MacLeod-Boynton chromaticity space showing chromaticities used in the experiments. Circles at the ends of a single line represent chromaticities of the square wave modulation used in the experiments (always symmetric around equal-energy-spectrum “white” at the center of the diagram). Four axes of chromatic modulation are shown. The vertical and the horizontal axes are referred to as cardinal axes (Derrington et al., ). The two diagonals are referred to as intermediate axes.

(a) Schematic diagram of the experimental arrangement. (b) Example of a possible fused percept with stable perception of a lime-colored disc (corresponding to the chromaticity at 270° in the MacLeod and Boynton chromaticity space in ).

Didactic graph with a cumulative survival-style plot that will be used to present results from Experiment 1 (and 2 and 5). The plot above is for one participant (A.D.D.) with chromaticities switching along the S/(L + M) axis in Experiment 1. See the main text for an explanation of how to interpret the plot.

Results from the experiment with chromatic interocular-switch rivalry along cardinal axes, plotted using the conventions in . All measurements with modulation along each of the cardinal directions are shown, for each of the three observers (A.D.D., J.H.C., and W.W.). The top panels are for modulation between chromaticities at 0° and 180° (l-axis). The bottom panels are for modulation between chromaticities at 90° and 270° (s-axis). Each of the six panels contains three cumulative survival-style plots showing the proportion of time that the dominance duration of a uniformly colored disc was as long or longer than a given value on the horizontal axis.

The proportion of total viewing time perceiving a particular stable uniform color percept, with chromatic modulation along each of the cardinal directions (above, 0°–180 for three observers; below, 90°–270 for three observers). The interocular-switch frequency was 3.75 Hz, as indicated within each bar. The approximate perceived stable color is indicated by the bar's color. Error bars show SEMs (SEM less than 0.02 where not plotted). Values replotted from .

The proportion of total viewing time for which each stable uniform color was perceived (approximate perceived hue shown by bar color), with chromatic modulation along each of the cardinal directions (0°–180° above, 90°–270° below). Measurements for two observers were taken at 3.13, 3.75, 4.69, and 6.25 Hz (frequency indicated by label within each bar). Error bars show SEMs (SEM less than 0.02 where not plotted).

Results from Experiment 5. As but for classic binocular color rivalry. Note that participant J.H.C. never experienced the color corresponding to the chromaticity at 180°, so there is no plot for that chromaticity in the top middle panel.